The present invention relates to copper base alloys having utility in electrical applications and to a process for producing said copper base alloys.
There are a number of copper base alloys that are used in connector, lead frame and other electrical applications because their special properties are well suited for these applications. Despite the existence of these alloys, there remains a need for copper base alloys that can be used in applications that require high yield strength greater than 80 KSI, together with good forming properties that allow one to make 180xc2x0 badway bends with a R/T ratio of 1 or less plus low relaxation of stress at elevated temperatures and freedom of stress corrosion cracking. Alloys presently available do not meet all of these requirements or have high costs that make them less economical in the marketplace or have other significant drawbacks. It remains highly desirable to develop a copper base alloy satisfying the foregoing goals.
Beryllium copper generally has very high strength and conductivity along with good stress relaxation characteristics; however, these materials are limited in their forming ability. One such limitation is the difficulty with 180xc2x0 badway bends. In addition, they are very expensive and often require extra heat treatment after preparation of a desired part. Naturally, this adds even further to the cost.
Phosphor bronze materials are inexpensive alloys with good strength and excellent forming properties. They are widely used in the electronic and telecommunications industries. However, they tend to be undesirable where they are required to conduct very high current under very high temperature conditions, for example under conditions found in automotive applications for use under the hood. This combined with their high thermal stress relaxation rate makes these materials less suitable for many applications.
High copper, high conductivity alloys also have many desirable properties, but generally do not have mechanical strength desired for numerous applications. Typical ones of these alloys include, but are not limited to, copper alloys 110, 122, 192 and 194.
Representative prior art patents include U.S. Pat. Nos. 4,666,667, 4,627,960, 2,062,427, 4,605,532, 4,586,967, 4,822,562, and 4,935,076.
Accordingly, it is highly desirable to develop copper base alloys having a combination of desirable properties making them eminently suitable for many applications.
In accordance with the present invention, it has been found that the foregoing objective is readily obtained.
Copper base alloys in accordance with the present invention consist essentially of tin in an amount from about 0.1 to about 1.5%, preferably from about 0.4 to 0.9%, phosphorous in an amount from about 0.01 to about 0.35%, preferably from about 0.01% to about 0.1%, iron in an amount from about 0.01% to about 0.8%, preferably from about 0.05% to about 0.25%, zinc in an amount from about 1.0 to about 15%, preferably from about 6.0 to about 12.0%, and the balance essentially copper. It is particularly advantageous to include nickel and/or cobalt in an amount up to about 0.5% each, preferably in an amount from about 0.001% to about 0.5% each. Alloys in accordance with the present invention may also include up to 0.1% each of aluminum, silver, boron, beryllium, calcium, chromium, indium, lithium, magnesium, manganese, lead, silicon, antimony, titanium, and zirconium. As used herein, the percentages are weight percentages.
It is desirable and advantageous in the alloys of the present invention to provide phosphide particles of iron and/or nickel and/or magnesium or a combination thereof, uniformly distributed throughout the matrix since these particles serve to increase strength, conductivity, and stress relaxation characteristics of the alloys. The phosphide particles may have a particle size of 50 Angstroms to about 0.5 microns and may include a finer component and a coarser component. The finer component may have a particle size ranging from about 50 to 250 Angstroms, preferably from about 50 to 200 Angstroms. The coarser component may have a particle size generally from 0.075 to 0.5 microns, preferably from 0.075 to 0.125 microns.
The alloys of the present invention enjoy a variety of excellent properties making them eminently suitable for use as connectors, lead frames, springs and other electrical applications. The alloys should have an excellent and unusual combination of mechanical strength, formability, thermal and electrical conductivities, and stress relaxation properties.
The process of the present invention comprises: casting a copper base alloy having a composition as aforesaid; homogenizing at least once for at least one hour at temperatures from about 1000 to 1450xc2x0 F.; rolling to finish gauge including at least one process anneal for at least one hour at 650 to 1200xc2x0 F.; and stress relief annealing for at least one hour at a temperature in the range of 300 to 600xc2x0 F., thereby obtaining a copper alloy including phosphide particles uniformly distributed throughout the matrix. Nickel and/or cobalt may be included in the alloy as above.